Ostiolar Hyphae Research Articles

A new Ophiostoma species associated with bark beetles infesting Norway spruce

During a survey of fungi associated with bark beetles in Germany, an undescribed species of Ophiostoma was isolated that differs from the other species of the genus by having pigmented, aseptate, convergent ostiolar hyphae, cucullate, sheathed ascospores, and a Hyalorhinocladiella anamorph. The species is described as Ophiostoma neglectum Kirschner & Oberwinkler. It is rarely associated with primary bark beetles but often associated with secondary bark beetles mainly infesting Norway spruce.Key words: Ophiostoma neglectum, Hyalorhinocladiella, secondary bark beetles, Picea abies, Pinus sylvestris, conidial development.

A New Ceratocystis Species Defined Using Morphological and Ribosomal DNA Sequence Comparisons

A Ceratocystis Ell. & Halst. species has recently been reported from Acacia mearnsii De Willd. in South Africa showing symptoms of die-back and gummosis. The fungus was tentatively identified as Ceratocystis fimbriata Ell. & Halst. that is a well-known and notorious pathogen of many plants of the world. The fungus from A. mearnsii, however, differs morphologically from authentic C. fimbriata isolates. In this study, isolates from A. mearnsii in South Africa were compared with C. fimbriata isolates from different geographic areas on the basis of morphology and ribosomal RNA (rRNA) sequence data. Morphological comparisons showed that the Ceratocystis isolates from A. mearnsii have light-coloured perithecial bases and divergently arranged ostiolar hyphae compared with entirely black perithecia and convergently arranged ostiolar hyphae of typical C. fimbriata isolates. Comparisons of rDNA confirmed the morphological differences and grouped the South African isolates apart from C. fimbriata originating from other areas. This important pathogenic fungus is consequently described as new.

Ceratocystiopsis Proteae Sp. Nov., with a New Anamorph Genus

A new species, Ceratocystiopsis proteae, collected from insect-infested Protea repens is described. Knoxdariesia, a new genus of dematiaceous hyphomycctcs is described to accommodate the anamorph of C. proteae. Ceratocystiopsis proteae shares characteristics of Ceratocystis sensu stricto (cycloheximide sensitivity), Ceratocystiopsis (falcate ascopores) and Ophiostoma (relatively long pcrithecial necks, divergent ostiolar hyphae and an anamorph with holoblastic conidium development) but is currently best accommodated in Ceratocystiopsis. Knoxdaviesia pfllteae superficially resembles the hyphomycete genera Leptographium and Stachybotrys. This is the first species ofOphiostomataceae described from an indigenous plant in southern Africa and its relationship with other Ophiostomataceae is discussed.

Sexual Compatibility, Morphology, Physiology, Pathogenicity and in vitro Sensitivity to Fungicides of Thielaviopsis paradoxa Infecting Sugarcane and Pineapple in Puerto Rico

A previously unreported race of Thielaviopsis paradoxa was isolated from pineapple fruits with symptoms of black rot disease. Macro- and microconidia resemble in appearance those of T. paradoxa, the causal agent of the pineapple disease of sugarcane. Perithecia were produced in PDA (24°-28° C.) when the pineapple isolate was crossed with the light strain of T. paradoxa from sugarcane. Perithecia are characteristic of Ceratocystis paradoxa (horn-like appendages on the base of the perithecia and long, pointed ostiolar hyphae) and are morphologically indistinguishable from those obtained by crossing two sexually compatible strains from sugarcane. However, the rate of growth of the pineapple isolate, under various temperatures, pHs, and cultural media, was consistently different from those characterizing other strains of the fungus. The pineapple strain attacks sugarcane seedpieces more virulently than isolates obtained from sugarcane. In vitro tests were conducted in the laboratory to determine the relative toxicity of the fungicides benzoic acid, Dowicide A, Benlate, Tecto 60 (TBZ), and Dithane M-45 on pineapple and sugarcane isolates of the fungus. Benzoic acid and Dowicide A appeared to be the most effective of these fungicides for inhibiting mycelial growth of T. paradoxa.

In Vitro Formation of Sexual Stage of Thielaviopsis paradoxa from Sugarcane in Puerto Rico

Two strains of Thielaviopsis paradoxa, one light and one dark, were isolated from diseased cuttings of sugarcane in Puerto Rico. Perithecia were produced when the dark strain was crossed with the light strain in potato dextrose agar medium at 24° to 28° C. The perithecia obtained are characteristic of Ceratocystis paradoxa (horn-like appendages on the base of the perithecia and long, pointed ostiolar hyphae). Ascospore isolations consistently resulted in the recovery of typical T. paradoxa culture. No perithecia were produced when cultures of the same isolates were crossed. This constitutes the first report on formation of the sexual stage of T. paradoxa from sugarcane in vitro.

CULTURAL STUDIES OF SEXUAL REPRODUCTION OF CERATOCYSTIS FAGACEARUM

The optimum KH2PO4 concentration for perithecium production by Ceratocystis fagacearum in a semi-synthetic agar medium was 7.4 × 10−1 M. A great reduction in the number of perithecia occurred at 0.1 M and none were formed at 0.2 M concentration. The optimum pH was 5.2 and no perithecia formed at pH 7.0. Either exogenous thiamine or its pyrimidine moiety is absolutely essential for perithecium formation. Pyridoxine, inositol and biotin were not required for growth or reproduction. Receptivity of 14-day-old cultures remained high for longer periods when stored at 12 °C than at 3 °C or 21 °C. Of the 17 isolates studied, 14 produced sterile perithecia before conidia were applied experimentally. Attempts to fertilize these were unsuccessful. Perithecia which did not extrude ascospores formed on colonies following application of conidia. In such perithecia, opened ostiolar hyphae did not necessarily indicate sterility. Neither abrasion of colonies, nor brushing with sterile distilled water or with a filtrate of sonic-disrupted condia, increased sterile perithecium production. However, brushing the colonies with an extract of germinated conidia did increase their formation.

NEW SPECIES OF THE GENUS CERATOCYSTIS

A study of the species of Ceratocystis found in Ontario on decaying slash has been made and most of the species grown in pure culture. The characteristics of the genus and the separation of species are discussed. Four species found on wood of coniferous trees are described as new. Illustrations are included for all of these. Ceratocystis brunneocrinita Wright and Cain is described from several collections of Abies balsamea. The perithecia have brown ostiolar hyphae and the ascospores appear rectangular. Ceratocystis europhioides Wright and Cain, on Pinus and Picea, has ascospores similar to but larger than the nonostiolate Europhium trinacriforme Parker. Ceratocystis falcata Wright and Cain, on Pinus, resembles Ceratocystis minuta (Siem.) Hunt but is distinguished by the longer, septate ascospores. Ceratocystis sagmatospora Wright and Cain, on Pinus and Picea, has saddle-shaped ascospores with elaborate gelatinous sheaths.